“Space appendages” means space equipment designed to be deployed in space, such as solar generators or antennas for example. The invention consists of a simple and robust solution allowing the smooth release of such space appendages.
The function of this type of system is initially to hold in a stowed position one or more space appendages, that is to say in general movable elements that can be deployed on either side of the body of the satellite and, secondly, to release the said appendages smoothly. The invention relates mainly, but not exclusively, to the situation in which the space appendages are solar generators. The system for holding in the stowed position and for releasing the appendages conventionally mainly consists of a separation nut and a tie-rod placed in tension. In practice, in the known systems, the tie-rod participates, with the nut, in tensioning a series of stacked elements, such as solar generators folded one on top of the other for the purpose of minimizing the volume of the satellite for the purpose of the launch, and allowing the launch loads to pass by friction.
However, it is known that, in this type of device, the tie-rod has geometric defects which can be considerable, in particular if the number of stacked elements is high. As shown in FIG. 2, the said geometric defects may be defects of inclination or of displacement for example. These geometric defects may cause dynamic defects resulting in radial forces or clamping moments being exerted at the ends of the tie-rod.
Failure to take account of these defects may cause serious malfunctions which may go as far as the failure of the space appendages to deploy and therefore possibly involving loss of the mission.
Another known problem lies in the impact that can occur when the tie-rod is released. The nut device mentioned above is responsible for releasing the tie-rod. The said tie-rod is, at the moment of its release, in a stressed state and its sudden release can cause impacts that can damage the space appendages or the satellite itself. In the context of certain current devices, the problem doubles. Specifically, initially the tie-rod is released by a pyrotechnic lock the explosion of which causes a first impact. Then, with the tie-rod being under tension before being released, its sudden release, already mentioned, can cause damage to the space appendages or to the carrying structure. For the purpose of minimizing this problem, “low shock” nuts have been developed. This type of complex nut is usually a one-shot nut and can be reconditioned. However, the “low shock” ability of these nuts applies only to triggering the release of the tie-rod and not to the release of the appendages as such. Specifically, the geometric defects of the tie-rod are not really compensated for and, particularly if the tie-rod has large dimensions, there is still a sudden expansion of the tie-rod that can cause an impact that is sometimes considerable, the tie-rod hitting the space appendages. This is explained notably by the fact that the release of the stressed tie-rod remains sensitive to the angular deviations of the said tie-rod.
In summary, there is no satisfactory solution in the prior art for overcoming the geometric defects of the tie-rod and for allowing its smooth release. The invention proposes a simple and robust solution to solve this dual problem. It lies essentially in the use of an active tie-rod device controlled by means of a heater inside or outside the said tie-rod.